A new reagent for polypeptide synthesis: mu-oxo-bis-(tris-(dimethylamino)-phosphonium)-bis-tetrafluoroborate.

The products 1 and 2 (X = OTs) have been isolated from the reaction between hexamethylphosphortriamide and p-toluene sulfonic anhydride and the latter converted into μ-oxo-bis-tris-(dimethylamino)-phosphonium]-bis-tetrafluoroborate 2 (X = BF₄). This is a practical reagent for the formation of the peptide link. Where racemisation is possible via oxazolone formation this can be decreased by the addition of 1-hydroxybenzotriazole or N-hydroxysuccinimide. These additives may also increase the efficiency of condensation at glycine and proline residues.